The commands to copy a saved configuration to RAM on Cisco devices are:
copy startup-config running-config: This command is used to copy the startup configuration (saved configuration) into the running configuration (current configuration in RAM). It is typically used when you want to restore the device to a previously saved configuration after changes have been made1.
copy tftp running-config: This command allows you to copy a configuration file from a TFTP server directly into the running configuration of the device. It's useful for applying a new configuration or for restoring a configuration from a backup located on a TFTP server1.
The other options listed are not valid for copying a saved configuration to RAM:
copy running-config startup-config copies the current running configuration to the startup configuration, which is the opposite of what's asked.
copy running-config tftp is used to save the running configuration to a TFTP server, not to copy to RAM.
copy tftp startup-config would copy a file from a TFTP server to the startup configuration, not to the running configuration in RAM.